Atari 520STFM Teardown + 4Mb Marpet Xtra RAM + TOS + Blitter Upgrade + HxC Floppy Emulator & More 

Hehe, I've been there myself!

I did exactly same thing 🤣

hardcore8uk Thanks! No, I've not heard of the Gryphon 030 - sounds like a Falcon 030 or something?

Thanks lol! I spent so much time repairing and supporting these systems back in the day (around 25+ years ago now).

Ah cool, I have an stfm in my parents roof space from my youth which doesn't read disks so I'm going to be using your videos quite a lot! Disk drives are going for about £20 posted on eBay so going to buy one ASAP. 😊

AtariBorn It's a two fold thing - you have to install a switch so one throw of the DPDT switch goes: - When ON it connects SIMM pin number 18 (A9) to the connector as normal - so its basically going to the A9 pin on the ST MMU. When its OFF, the connection from SIMM 18 (A9) is NOT connected to the connector going to the ST MMU - this sets the ST into thinking the SIMMS are 256Kb each, giving you 1Mb. On the other 'throw' of the switch (DPDT switch is used), when ON the central pin of the switch is connected to the ground and nowhere else, when OFF the ground (middle pin) should then connect to the SIMM 18 (A9), so basically its supplying a constant ground to the SIMM 18 (A9) pin when the A9 pin is isolated from the ST. The reason you need to do this is without forcing that A9 on the SIMM to ground it will be floating (not high, not low) and can and will flip state on its own causing crashes etc - it probably won't even boot.

Gotcha. I appreciate the info.

Not that I am aware of! I think the power supplies for these are region specific - I could be wrong though! Just inspect the PSU PCB and look for anything that says 220 / 110V

Hehe =D Power Supply tends to be the main issue in ST's. Occasionally you may get bad RAM, or a faulty Glue or Shifter chip. They are much more robust than Amigas though imho.

That's cool! I'm an Amiga man at heart (hey, easy on the tomato throwing) as I only had an Atari for about a year or two when I was 5 then it was swapped for an Amiga after, but I do have memories of it and wouldn't mind one for the first part of a "reliving the journey" (of my computing past) that I'm hoping to do :). Cap changes for PSUs no big deal... I've saved my share of monitors from landfill that way....

I've kept Amiga for Amiga Forever and stuck with ST for real hardware as it is better designed for the most part. The case and GUI look better too. The PSUs are iffy, not quite the Atari XL ingot, but the Meanwell RD50 and 60 are small enough to fit. The 50 requires off the shelf cable. The 60 requires a 3 prong jack that isn't cheap to obtain, but the tradeoff is smaller size for the same power output. And the amperage is definitely needed if add-ons like memory are to be added as the 5v rail on the original is 3A. Meanwell's is 6A for the 5v rail and that's better than plenty!

I will try and look at that soon (when I look at an STFM sat here waiting). There are some utils on the PP Atari ST website, one that will split a ROM for you.

Check out the 4MB upgrades that Exxos sells!

I ask only as I saw another brand of ram upgrade taking r59 out as well, which seems weird. The Marpet original manual only says 60 and 61.

I honestly cannot remember much about this mod! I will take a look soon when I do more upgrades and things to this ST!

I haven't, but I will cover it at some point soon! I need to do some things to my ST and will perhaps cover it then.

I use it with a HDD, there are thousands of games converted to run from HDD (See Atari PP Adapted Games) in Google). Those make use of RAM above 1MB.

@@GadgetUK164 Oh, so it is basically like whdload, that requires some ram

@@Kppot Yes =D The game assets get cached =D PP's HDD adapted versions of ST games often use 2MB or more - just speeds everything up and makes it run well from HDD.

No - the PSU can be a bit tricky to remove! I didn't explain very well in that video at all, you have to kind of tilt it and massage it out - it's a bit awkward to do!

Thanks! Yes, some strange design choices by Atari! I never like having the PSU internal - due to heat and noise etc. But it's also a shock risk if anything gets spilled over the ST. These days that probably wouldn't be allowed to be sold lol

I will try and do a video on this at some point! I had planned to do one related to the Ultra Satan - that's a better purchase than the SD floppy drive imo. Because you can copy games onto the SD still, but they run much faster etc. If you haven't already, check out PP's hard disk adaptions here:- atari.8bitchip.info/fromhd.php And if you do get an Ultra Satan (HDD rather than FDD), you can get PP's hard disk driver from that website too - it's pretty cheap, something like 15 or 20 euros I think.

Great job =D Another ST saved!!!

The tiny screws underneath the keyboard - I think there might be one or two longer ones but most of them are the same size. On the case there are a few different lengths I think. It has been a while since I took an ST to pieces.

GadgetUK164 I had a feeling you might say that. Best I get my magnetic mat out when I do it then! Many thanks, Dave

Thanks, I cannot do repairs for other people due to a long term health problem. If you are based in the UK you might be able to get it repaired by 'Dave Curran' at tymemouth software? I suspect I know what's wrong with it, and might have a spare part if Dave needs it. Those monitors provided power to the base unit, and they had large chips stuck to a heat sink (I cannot remember the correct name of the package body of the chip) - often their part numbers started STK. Those are what failed all the time in those old Amstrad monitors. It was so common that when I was in the industry we started adding 12v fans inside the monitor to cool the heat sinked 'STK' chips.

Sorry - typo there "Tynemouth Software" www.tynemouthsoftware.co.uk/

Isn't there a 4MB limit for the ST and STe? It must be ALT-RAM or something? Quite rare I would think!

From what I've read it seems to trick tos into thinking it's a TT, so it's probably seen as alt-ram for a total of 12Mb. The 68k is able to address 16Mb i think. I don't have an STe any more so I can't test it.

From my experience, there is a relationship between capacitance and ESR. When its capacitance is spot on, it's rare the ESR is out - it can happen, but I've found it to be rare. I've been collecting every single cap I've removed from things over the last 4 years or so., and I will be covering that in a video at some point.

​@@GadgetUK164 So how do you know when a capacitor is stuffed and behaving like a conductor and putting DC bias on a rail where it shouldn't be?

Obviously its a good idea to check the ESR if you can! I will be recapping the motherboard on that ST soon - will check the ESR on each I remove, but I am betting they are probably all OK. The sheer volume of caps I've replaced over the last 4 or 5 years is staggering, and in all cases where I replaced them for the hell of it - all the ones on the board were all still fine. There are places cap fail more (eg. PSUs) and there are bad brands etc, but there are far too many people thinking that you must always swap out every single electrolytic in a system.

Yes, on more recent videos I stay well away from the carpet =D It's a case of when I worked in the trade I always worked off ESD mats with a wrist strap, but 30 years later I got lazy when I first started working on my own stuff. I've taken the feedback along the way and corrected my ways.

@@GadgetUK164 Handy hint is you can usually ground your static just by touching the shielding in the case, its not the right way to do it but its an old trick, hence why you were fine doing what you did. p.s where did you get your 4Mb Marpet Xtra RAM from? wouldn't mind doing that mod on my 520stfm

It is a standard Atari ST with a couple of upgrades. I use the HxC floppy emulator (uses SD card) from Lotharek (search for Lotharek in google). I also have an "Ultra Satan" which is an external HDD for the ST - that provides 2 x SD card slots for virtual HDDs.

Yes, that's a good point! Never had a problem with ST connectors breaking - or wires detaching etc, but you raise a valid point! I have had that problem recently on a Saturn CD connector where I had to remove the pin resolder a wire and fit it back into the connector. No permenant damage but it was a pain!

Sorry I missed this message somehow!! There should be two wires which have clips on both sides, and you connect one end to the 5v and the other to a pin on a resistor which I think you need to lift or cut. That disables the on board RAM.

+Amy Marie Yes it does! Jeff has produced an updated firmware that uses the HxC interface.

Sweet!, thanks

Haha, that's sweet lol! Never would have thought of using a +3 PSU to power an ST =)

Thanks for the positive comments and for watching and commenting btw =)

Thanks =)

Thanks =)

Thanks! It was a bit of a messy chaotic video, I tend to not plan these things - just dive in and it ends up being inaccurate in places etc =|

Hi! Thanks for the nice comments =) I will be doing some work on my ST this weekend so I will do a video for you whilst I am in there, to show you which chips to press down on. All you need to do is press down on the chips which are in sockets. The RAM (top left), 16 of them are soldered straight to the board - so you cant do anything with those) but any chips that have a black plastic socket under them - those are the chips you want to 're-seat' rather than take the chips out and put them back in the first thing to do is just press down on each of them. Sometimes they will make a small click or creak as they move back into their sockets. With time and heat they creep out of the sockets a little. The main ones that could be causing your problem are the square chips with a socket around their edges. Just press down in the centre with your thumb to make sure they are down in the sockets OK. There's a chip (video shifter chip) in the silver shielded can in the middle, so you will have to bend the little clips on the metal casing there to lift the lid so you can access that chip - again just press down on it to make sure its firmly down in the socket.

Truly grateful to you my friend ,I will have a go at what you suggest and your videos are superb for those of us who are not too well up with the workings of the Atari so I keep watching them over and over again ,lol my very best wishes and thanks Brian.

mrmusdtard2 Hi, i've uploaded a short video explaining about the chip reseating!